Scene clip in Video Editor affects the image strip above it
I submitted a false bug report on this issue and a developer, Sergey, explained the problem: Color Management had been turned off.

Color management is on by default, and Sergey suggests not messing with it.  (someone else edited my .blend file)

To re-enable Color Management, go to the Scene tab of the Properties window and under Display Device, select sRGB.



The problem should be gone.  Please see the bug report for details on why this occurs.